No abstract

Since the serial discontinuity concept (SDC) of rivers is proposed, few studies have tested it in a highly fragmented river ecosystem. In this study, environmental factors, phytoplankton species richness, and SDC predictions were demonstrated along the 13 cascade dams in a subtropical river (China). Our results indicated that among environmental factors, water temperature and transparency have seasonal differences, and river width has spatial differences; total species richness (TSR) increases from upstream to downstream, and distance is the reason for its variation. In addition, TSR also has spatial variations in each cascade dam, with the maximum or minimum value of each cascade section often occurring near the dam. A predictive model was constructed and revealed that seasonal differences in species richness were more significant than spatial differences, which were mainly observed during wet periods. Taken together, these results suggest that the construction of cascading dams enhances spatial differences in phytoplankton species richness, especially during periods of abundant water. In addition, environmental parameters such as water temperature, pH, and DO and TSR all support SDC predictions. In the future, we will continue to investigate this aquatic ecosystem to study more phytoplankton-related indices affected by the cascade damming, and hope to fully validate the SDC predictions.